Somaliland Secondary School Biology Notes
Human Health and Diseases- Form 4 Biology Notes
Health
What is health?
- Health is defined as the physical, mental and social state of a person.
- Health is a state of complete physical, mental and social well-being.
Traits of Good and Poor Health
The below table shows the difference between the traits of good health and poor health
| Traits of Good Health | Traits of Poor Health |
|---|---|
| Physically fit | Physically unfit |
| Optimistic (has a positive outlook on life) | Pessimistic (has negative outlook in life) |
| Respects norms, values and traditions of the society. (well-adjusted in society) | Violates norms, values and traditions of the society. |
| Can undertake mental and physical tasks, without too much difficulty. | Cannot undertake mental and physical tasks. |
Diseases
What is disease?
- Disease is a disorder or bad functioning (malfunction of mind or body) which leads to departure of good health.
- Disease is a disorder or malfunction of the mind or body, which destroys good health.
Extrinsic and Intrinsic Factors (Disease Causing Factors)
What are the factors responsible for causing diseases?
Factors or agents that cause or influence disease to a person are;
- Extrinsic Factors (External Factors)
- Intrinsic Factors (Internal Factors)
Extrinsic factors are disease causing factors which exist outside the human body (or enter the body from outside the body).
Examples of extrinsic factors are including;
- Pathogens
- Nutritional factor (unbalanced diet)
- Environmental pollutants, and
- Drug addictions
Intrinsic factors are disease causing factors which exist in the human body.
Examples of intrisic factors are including;
- Hormonal disturbance
- Genetic abnormalities (Genetic disorder)
- Malfunction of the immune system, and
- Improper functioning of parts or organs of the body
Unifactorial and Multifactorial Causing Diseases
Diseases may have either single cause or different causes, which can either be;
- Unifactorial (single factorial)
- Mutifactorial
Unifactorial disease is a type of disease caused by a single factor (has a single cause) such as malaria.
Multifactorial disease is a type of disease caused by many factors (has many causes), such as heart diseases, cancer, high blood pressure and diabets.
Acute and Chronic Diseases
According to their duration, diseases can be differentiated into:
- Acute diseases
- Chronic diseases
Acute diseases are sudden onset diseases with rapid changes and last for a short time, such as common cold.
Chronic diseases are diseases that develop gradually and continue for months or years and last long, such as tuberculosis (TB).
Signs and Symptoms
Diseases are characterized or usually indicated by;
- Symptoms
- Signs
Symptoms are indications of diseases felt by a patient.
Signs are indications of diseases that can be detected or observed by another person or a doctor.
Categories of Diseases
Category | Description | Examples |
Physical diseases | Diseases that cause temporary or permanent damage to the body or part of the body | Leprosy, broken leg, bone fracture |
Infectious disease | Diseases caused by pathogens and can be transmitted from person to person or from animal to person. They are also called communicable diseases. | Malaria, cholera, tuberculosis, AIDS |
Non-infectious diseases | Diseases that are NOT caused by pathogens and cannot be transmitted from one person to another. They are also known as non- communicable diseases. | Sickle cell anemia, stroke, diabetes, heart diseases, hypertension |
Deficiency diseases (nutritional diseases) | Nutritional diseases are diseases caused by an inadequate or unbalanced diet. Deficiency diseases results from missing or short supply of essential nutrients. They are classified into:
| Scurvy, night blindness, rickets, anemia, kwashiorkor |
Inherited diseases (genetic diseases or genetic disorder) | Diseases are caused by faulty genes and can be passed only from parents to their children. | Hemophilia, cystic fibroses, sickle cell anemia |
Mental diseases | Diseases that affect a person's mind. Mental diseases are diseases caused by brain damage or psychological illness. | Creutzfeldt-Jakob disease (CJD), Alzheimer's, Dementia, Claustrophobia, schizophrenia, |
Degenerative diseases | Diseases caused by a gradual decline or loss of function in one or several organs of the body, often associated with ageing. | Osteoarthritis, coronary heart diseases, stroke, cancer, hearing and sight defects |
Social diseases | These are diseases influenced by person's social environment or people's living conditions and behavior. | Hypothermia, drug-addiction, unhealthy lifestyle. |
Self-inflicted diseases | Self-inflicted diseases are diseases caused by damage to a person's health by their own decisions and behavior. | Suicide, choice to smoke, misusing of drugs (alcoholism), and eating high fat diet. |
Epidemic, Endemic and Pandemic
Endemic
Endemic is a disease that is always present in a population. Example, tuberculosis and malaria. (En=in, demo from demos=people)
Epidemic
Epidemic is a disease that spreads rapidly to affect many people. Example, influenza (flu). (Epi =among, demo from demos=people)
Pandemic
Pandemic is a disease that spreads over large area, such as continent of worldwide. Example, AIDS and Corona-virus disease (COVID-19). (Pan=all, demo from demos=people).
Difference Between Infectious and Non-infectious Diseases
The below table shows the difference between Infectious and Non-infectious Diseases.
| Infectious Diseases | Non-infectious Diseases |
|---|---|
| Infectious diseases (also called communicable diseases) are diseases that can spread from an infected person to a healthy person. | Non-infectious diseases (also called non-communicable diseases) are diseases that cannot be passed from one person to another. |
| Infectious diseases are caused by pathogens (viruses, bacteria, fungi). | Non-infectious diseases are not caused by pathogens. Non-infectious diseases are caused by:
|
| Examples of infectious diseases are; tuberculosis, cholera, influenza, AIDS, measles, etc. | Examples of non-infectious diseases are; hemophilia, heart diseases, diabetes, sickle cell anemia, cancer, hypertension, etc. |
Infectious Diseases
Infectious diseases are diseases which can be transmitted from one person to another (from infected person to a healthy person).
Infectious diseases are also called as communicable diseases or transmittable diseases.
Infectious diseases are any diseases caused by pathogenic microorganisms, such as bacteria, viruses, fungi, protozoa, and also worms & parasite.
What are pathogens?
Pathogens are organisms that cause disease to humans, animals and plants. (Pathogens are disease-causing organisms).
Pathogens that cause infectious diseases (communicable diseases) are viruses, bacteria, fungi, protozoa, or parasites.
Pathogens are also called microorganisms, microbes or germs.
Modes of Infectious Disease Transmission
The main ways through which communicable diseases (infectious diseases) spread from one host to another are including;
- Through air
- Through water
- Through food
- Insect vector
- Through physical contact
- Droplet spread (droplet infection)
- Through sexual contact
- Through animal bite
- Contact with soil
Airborne Diseases
Diseases that spread through air or dust are called airborne diseases.
Examples, influenza, tuberculosis, common cold, COVID-19.
Waterborne Diseases
Diseases that spread through contaminated water are called waterborne diseases. Examples, cholera, amoebic dysentery.
Foodborne Diseases
Diseases that spread through contaminated food are called food-borne diseases.
Examples, cholera, food poisoning, typhoid fever.
Vector-borne Diseases
Vector is any organisms (invertebrates) such as insects that carry germs and spread disease.
Diseases that spread through insects from one host to another are called vector-borne diseases. Examples, malaria, sleeping sickness, cholera.
Vectors can spread diseases into two ways: mechanical transmission and biological transmission.
Through Physical Contact
Diseases that spread through physical contact are called contagious diseases. Example, ring worms.
Droplet spread (droplet infection)
Droplet spread or droplet infection is a type of disease transmission which an infected person coughs or sneezes on another person and the healthy person inhales the mucus containing pathogen.
Examples, common cold, influenza, whooping cough, pneumonia.
Through Sexual Contact
Diseases that spread through sexual contact (sexual intercourse) are called sexually transmitted diseases (STD).Examples, syphilis, gonorrhea, AIDS
Through Animal Bite
Diseases that spread through the bite of a rabid animal are called animal-borne diseases or pet-borne diseases, e.g. rabies.
Through Contact with Soil
Diseases that spread through contact with contaminated soil are called soil-borne diseases, e.g. tetanus.
Bacterial Diseases
Bacteria are prokaryotic, unicellular microorganism that are found everywhere.
Bacteria are found in the soil, water and air.
Bacteria are also found on human skin and in the digestive tract.
Bacteria can enter the body through a cut in the skin, the respiratory tract or the digestive tract and cause infections or disease.
Basic Shapes of Bacteria
The basic shapes of bacteria are including;
- Bacilli (rod shaped)
- Cocci (spherical shaped)
- Spirilli (spiral shaped)
- Vibrio (coma-shaped)
Cholera
Pathogen | Vibrio cholerae |
Methods of transmission | Food-borne, water-borne |
Site of infection (Site of attack) | Walls of small intestine |
Symptoms | Severe diarrhea, loss of water and salt, dehydration and weakness |
Treatment | Rehydration and taking antibiotics like tetracycline |
Control | Drinking water should be chlorinated or boiled Keeping good hygiene |
Diphtheria
Pathogen | Corynebacterium diphtheria |
Methods of transmission | Through inhalation of cough droplets from an infected person |
Site of infection | Nose, throat and larynx (upper respiratory system) |
Symptoms | Sore throat, fever, swollen glands, nose and throat get blocked, difficult breathing. |
Treatment | Antibiotics such as penicillin |
Control | Vaccination (Babies should be given DPT vaccine) Avoid close contact with infected person Isolation of the infected child |
Whooping Cough
Pathogen | Bordetella pertussis |
Methods of transmission | Through inhalation of cough droplets from an infected child |
Site of infection | Upper respiratory system |
Symptoms | Mild sneezing, runny nose and fever. Later there is hard and dry cough, whooping or wheezing during inspiration and vomiting. Secondary bacterial infection leads to pneumonia. |
Control | Vaccination against whooping cough |
Treatment | Antibiotics like tetracycline |
Tuberculosis (TB)
Pathogen | Mycobacterium tuberculosis and mycobacterium bovis |
Methods of transmission | Airborne; via unpasteurized milk from cattle |
Site of attack | Lungs, lymph nodes, bones, stomach |
Symptoms | Racking cough, coughing blood, chest pain, shortness of breath, fever, sweating and weight loss |
Treatment | Antibiotics are administered as treatment BCG (Bacillus Calmette Guerin) vaccination is given to children as a preventive measure. |
Control | Avoid close contact with infected people Milk must be pasteurized Cattle with TB diseases must be eradicated Spitting in public places must be banned |
Pneumonia
Pathogen | Mycoplasma pneumoniae |
Methods of transmission | Through inhaling infected air |
Site of infection | Lungs |
Symptoms | Coughing sputum which occasionally contains blood Sore throat Headache and fever |
Treatment | Antibiotics like sulfonamides |
Control | Avoiding close contact with infected person |
Typhoid
Pathogen | Salmonella typhi |
Methods of transmission | Through ingestion contaminated water and food (Food-borne and waterborne) |
Site of infection | Intestines |
Symptoms | Fever, headache, sore throat Muscular pain, diarrhea, abdominal pain, vomiting and loss of appetite Abdominal pain, weakness and fatigue |
Treatment | Antibiotics like ampicillin |
Control | Keeping good hygiene To boil or chlorinate drinking water |
Tetanus (Lockjaw)
Pathogen | Clostridium tetani |
Transmission | Contaminated soil or objects with tetanus bacteria enter the body through cut or wounds (deep soil wound) |
Site of infection | Nervous system and body muscles |
Symptoms | Muscle spasms Spasms and stiffness in jaw muscles Stiffness of neck muscles Stiffness of abdominal muscles Difficulty in breathing and swallowing Fever |
Control | Avoid contaminated soil or objects and always by wearing protective food wears |
Treatment and prevention | Injection of tetanus toxoid Children are normally vaccinated against tetanus |
Botulism
Pathogen | Clostridium botulinum |
Methods of transmission | Through eating poorly processed home canned food |
Site of infection | Gastrointestinal tract |
Symptoms | Nausea, vomiting, abdominal pain, blurred vision, difficult breathing and muscle paralysis |
Treatment | A drug called an antitoxin |
Control | Properly processing of food and checking expire date before using food |
Syphilis
Pathogen | Treponema pallidum |
Methods of transmission | Through sexual intercourse (STD) |
Site of infection of pathogen | Reproductive organs (genitals) |
Symptoms | Rash on body, fever, headache, pain in bones and joints, sore throat, nervous problems, fatigue, hair loss, swollen lymph nodes |
Treatment | Antibiotics such as penicillin |
Control and prevention | Avoiding illegal sex and having examination before marriage |
Gonorrhea
Pathogen | Neisseria gonorrhoeae |
Methods of transmission | Through sexual intercourse (STD) |
Site of infection of pathogen | Reproductive organs (genitals) |
Symptoms | Painful urination (burning during urination) Whitish discharge from reproductive organs (genital) Rashes on palms and mild sore throat Pain in joints, Abdominal pain Bleeding between periods in females Pain or swelling in testicles in males |
Treatment | Taking antibiotics, such as ceftriaxone injection |
Control and prevention | - Avoiding illegal sex and having examination before marriage |
Salmonella Food Poisoning
Pathogen | Salmonella typhimurium, Salmonella enteritidis and some types of Escherichia coli |
Methods of transmission | Through eating meat or egg or drinking contaminated with the bacteria (contaminated food) |
Site of infection | Gastrointestinal tract (Alimentary canal) |
Symptoms | Diarrhea, vomiting, abdominal pain, nausea |
Control and prevention | Food must be cooked well and milk must be pasteurized well. Good hygiene |
Treatment | Taking more fluids (Rehydration) |
Viral Diseases
Viruses are smaller than bacteria and can reproduce only inside other cells.
Viruses consist of genetic material of DNA or RNA surrounded by a protective coat of protein.
Viruses do not produce toxins, but they damage the body cells they invade.
Viruses can infect all types of organisms such as animals, plants and even other microorganisms like bacteria.
Common Cold
Pathogen | rhinovirus |
Methods of transmission | Inhaling infected air droplets or contacts |
Site of infection | Respiratory tract |
Symptoms | Watering eyes, runny nose, swollen nasal membranes making it difficult to breathe through the nose, mild headache, sore throat, coughing |
Treatment | Drink plenty of fluids Take symptom relief like paracetamol, ibuprofen, etc |
Control | Avoiding close contact with infected ones |
Measles
Pathogen | Measles virus (Rubeola virus) |
Methods of transmission | Through inhaling infected air, physical contact |
Site of infection | Eyes, nose, throat, skin |
Symptoms | Fever, headache, sore throat, runny nose, inflammation of the eyes, cough, appearance of rashes on the body |
Control | Isolation of infected person Vaccination |
Influenza (flu)
Pathogen | Influenza virus (Influenza viruses A and B) |
Methods of transmission | Through airborne |
Site of infection | Lining of the throat and breathing passages |
Symptoms | Fever, headache, inflammation of the respiratory tract, sore throat, dry cough, muscle or body ache, fatigue, |
Treatment | Drink plenty of fluids Take symptom relief like paracetamol, ibuprofen, etc |
Control | Avoid close contact with infected ones |
Hepatitis A
Pathogen | Hepatitis A virus |
Methods of transmission | Contaminated water and food |
Site of infection | Liver |
Symptoms | Tiredness, loss of appetite, nausea, upset stomach, enlarged liver, jaundice (eyes and skin become yellowish), body ache, fatigue, belly pain, mild fever |
Control | Keeping good hygiene, chlorinating drinking water, avoid taking fat rich substances. |
Hepatitis B
Pathogen | Hepatitis B virus |
Methods of transmission | Through sexual contact, blood transfusion, sharing needles and syringes |
Site of infection | Liver |
Symptoms | Symptoms are similar to hepatitis A but more severe |
Control | Avoid illegal sex, checking blood before transfusion, avoiding sharing needles, taking hepatitis B vaccine |
Chickenpox
Pathogen | Chickenpox virus (voricella virus) |
Methods of transmission | Contact with infected person |
Site of infection | Skin |
Symptoms | Fever, headache, rash filled with fluid |
Control | Avoid close contact with infected ones, the patient should be kept in isolation, vaccination |
Smallpox
Pathogen | Variola virus (smallpox virus) |
Methods of transmission | Contact with infected person |
Site of infection | Skin |
Symptoms | Fever, headache, vomiting, backache, severe fatigue, rashes filled with fluid |
Control | Avoid close contact with infected ones, vaccination |
Mumps
Pathogen | Mumps virus (known as paramyxovirus) |
Methods of transmission | Inhaling infected air, direct contact with an infected person |
Site of infection | Salivary glands |
Symptoms | Chilly, headache, fever, swollen salivary glands, muscle ache, weakness, fatigue, loss of appetite |
Control | Avoid close contact with infected ones, vaccination |
AIDS (Acquired immune deficiency syndrome)
Pathogen | Human immunodeficiency virus (HIV) |
Methods of transmission | Sexual intercourse (STD) Transfusion of infected blood Sharing contaminated needles and syringes Mother to fetus across placenta Mother to infant in breast feeding |
Site of action of pathogen | Immune cells (such as T-helper cells and macrophages) |
Symptoms | Flu-like symptoms, AIDS-opportunistic infections; including pneumonia, TB and cancer. Weight loss, diarrhea, fever, sweating and Mental disease (dementia) |
Method of diagnosis | Blood test for antibodies to HIV |
Control and prevention | Avoid unlawful sexual intercourse Avoid sharing used needles, syringes and razors Checking blood transfusion to the patient |
Poliomyelitis (Polio)
Pathogen | Virus (polio virus) |
Methods of transmission | Contaminated food and water |
Site of infection | First it attacks the intestines and later spreads to the nervous system |
Symptoms | Fever, headache, stiffness of neck and finally muscle paralysis and brain damage |
Control | Polio vaccine drop (oral polio vaccine, OPV) are given to children Keeping good hygiene |
Protozoa Diseases
Protozoa are single-celled organisms.
Some of the protozoa are parasites which live on or inside another organism and cause harm to the host.
Parasitic protozoa cause diseases to human, for example, food contaminated with protozoa can cause amoebic dysentery to humans. Also malaria is a disease caused by protozoa which are passed to human by the female anopheles mosquito.
Amoebic Dysentery
Pathogen | Entamoeba histolytica |
Methods of transmission | Water borne and food borne (contaminated water and food) |
Site of infection | Lining of the intestine |
Symptoms | Feeling of abdominal pain and nausea Formation of ulcers in intestine Diarrhea and vomiting Dehydration and faeces with blood |
Control and treatment | Proper sanitation should be maintained Wash hands properly after toilet and before eating or handling food Vegetables and fruits must be properly washed before eating To boil or chlorinate the water Cook food thoroughly Antibiotics may be given to the patients |
Malaria
Pathogen | Plasmodium (Plasmodium falciparum, P. Vivax, P. Ovule, P. malaria) |
Methods of transmission | Through the bites of infected female anopheles mosquito (insect vector) |
Site of infection | Liver, red blood cells, brain |
Symptoms | Fever, anemia, nausea, headache, muscle and joint pain, backache, shivering, enlarged spleen |
Control | Use of mosquito net and mosquito repellents Spraying stagnant water Clearing bushes |
Treatment | Anti-malarial drugs should be taken such as chloroquine, doxycycline, quinine,· mefloquine |
Fungal Diseases
Fungal infection is a skin disease caused by a fungus, which can affect one area of the body or many areas of the body, such as the skin, nails, mouth, feet, areas with skin folds such as the groin and also thighs.
Fungi cause irritating and contagious diseases to humans.
Fungal infections or infections of the skin including, athlete's foot, jock itch and ringworm are called fungal diseases.
Athlete's Foot
Athlete's foot, also called tinea pedis, is a fungal infection of the feet.
Transmission: physical contact (sharing foot wears, longtime wearing of socks, walking barefoot in toilets or public bathrooms).
Site of attack: foot
Symptoms: itching, peeling, redness, burning, blisters and sores
Control: regular washing of feet, regular changing of socks, avoid sharing foot wears, do not walk barefoot in wet areas.
Treatment: antifungal drugs, such as Griseofulvin.
Jock Itch
Jock itch, also called tinea cruris, is a common skin infection caused by a type of fungus called tinea.
Transmission: physical contact or indirect contact from objects carrying the fungus.
Site of attack: warm and moist areas of the body, genitals, inner thighs
Symptoms: itchy rash, redness, peeling or cracking skin, changes of skin color, and the affected areas can be scaly.
Control: keep the affected area clean and dry, wear clean clothes (regularly changing the underwear), do not share personal items
Treatment: antifungal drugs, such as Griseofulvin.
Ringworm of the Scalp
Ringworm of the scalp, also called tinea capitis is a fungal infection of the scalp and hair.
Transmission: physical contact, sharing combs and pillows.
Site of attack:scalp
Symptoms: scaly circular bands on the head, itchy, scaly and bald patch on the head; the infected patch spreads outward and heals at the center forming ring appearance.
Control: avoid sharing combs and pillows with other people; and Keep proper hygiene of the head
Treatment: antifungal drugs, such as Griseofulvin.
Candidiasis
Candidiasis is a disease caused by yeast-like fungi called candida.
They occur when yeast on the skin grows more actively and causes a red, scaling, itchy rash on the skin. Yeast infections or candida infections are not usually contagious.
Candidiasis or yeast infection may affect nearly any skin surface on the body, but are most likely to occur in warm, moist, creased areas including the armpits and groin, and it can also affects the mouth.
Candida can cause diaper rash in infants, infections of the nail, oral thrush in the mouth and also it causes vaginal yeast infection.
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Where are the other diseases dear teacher?
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